Oxidizers are commonly used to effectively destroy organic and inorganic contaminants. Some of the typical applications of oxidizers include treatment of water systems and inactivation of bacteria and viruses in various media.
Although oxidizers are used in numerous applications, there are also applications where they are not used even though their utility is well established. The reason these oxidizers are not used often relates to their instability during storage. Oxidizers such as hypochlorous acid and peracids, for example, could be used in more applications than the disinfection applications that they are already used in if their stability can be improved. The problem with some of these powerful oxidizers such as hypochlorous acid and peracids is that their activity level tends to decrease during storage. Since the effectiveness of the oxidizers in various applications depends on their concentrations, activity levels, and the level of demand on the oxidizer as measured by its oxidation reduction potential (ORP), a reduction in the activity level of the oxidizers impedes their performance in the various applications. Thus, even if an oxidizer is initially highly effective, the effectiveness decreases during storage.
A few methods are currently used to get around this storage problem. One of these methods, which is the point-of-use generation method or the in-situ method, is desirable because it eliminates the need for prolonged storage. However, on a practical level, these point-of-use generation methods are not widely employed because they require expensive equipment and specialized expertise. Other in-situ generation methods involve adding the reagents to the water to produce the target product. However, when doing this, significant dilution of reagents as well as competing reactions impede the level of conversion to the target product.
Sometimes, the reagents are coated to provide a barrier between the reagents and the environmental elements, thereby making the reagents easier to store and use in formulations. The coatings are designed so that when they are combined with water, they dissolve and rapidly release the reagents. Silicates, for example, are widely used in laundry detergent applications. In the alkaline condition induced by the laundry formulation, the silicate coating rapidly dissociates and releases the encased additives into the bulk water. There are also instances where a highly hydrophobic coating such as a wax or slow-dissolving coating is used for time-release purposes. These cases operate on the basis of a mechanism similar to the mechanism of the silicate coating in that the outer coating material quickly dissolves to expose the enclosed material to the solvent in the environment, at which point chemical reaction starts.
Various bleaching and oxidizing compositions have been made to enhance the performance in an application. Such enhancement is desirable because the generally effective hydrogen peroxide donors such as percarbonate, perborate, and persulfate-based additives do not remove stubborn stains from clothing. To enhance their bleaching ability under the conditions that are typical to the application (e.g., laundry water), precursors are added to induce formation of a more effective bleaching agents (e.g., tetraacetyl-ethylenediamine (TAED)) in-situ. However, this addition of bleaching agent precursors has its disadvantages. For example, high concentrations of additives are needed to achieve effective results, increasing both the cost and inconvenience.
Another way of enhancing peroxygen compounds' performance is to make them more stable, thus allowing long-term storage. Sometimes, the peroxygen compounds and the formulations they are used in are coated to enhance storage stability. These coatings, however, do not always dissolve quickly and therefore increase the time it takes for the peroxygen compound to become effective. One of the ways to allow long-term storage of oxidizers such as potassium monopersulfate and chlorine is to store them in packages or bags. The packages or bags are designed to dissolve in water, so that they can be directly thrown into a body of water. Although the use of bags provides for easy application in large scale or macro applications, their utility is limited in that they can be used only for applications of a certain scale.
A method of stabilizing reactive components for storage without compromising or limiting their performance during usage is desired.